The invention relates to a prober for testing devices in a repeat structure on a substrate having a probe holder plate, probe holders, on which a test probe is situated, which are each displaceable via a manipulator connected to a probe holder, and a substrate carrier on which the substrate may be fixed.
The invention also relates to a method for testing devices in a repeat structure on a substrate, in which needle tips of test probes are each positioned using a manipulator on a probe holder in relation to test contacts on the device, one first device is tested, and subsequently the test probes are positioned in relation to test contacts on a second device and the second device is tested.
Probers and methods for testing devices, which have a lower frame, over which a probe holder plate is situated at a distance to accommodate test probes, which contact the devices to be tested, are known. A movement unit is connected to the frame, on which a substrate carrier is situated within the distance spacing between frame and probe holder plate. The probe holder plate is provided with an opening, below which the substrate carrier is implemented as movable.
Probers of this type are used for testing devices, such as semiconductor chips in the wafer composite. The semiconductor wafers are laid on the substrate carrier and clamped fixed on the substrate carrier. The semiconductor wafers thus clamped are tested chip by chip in that contact islands located on the chip are contacted and impinged using measuring signals and the reaction to these measuring signals is measured or established. Test probes are provided for contacting the contact islands. These test probes are pre-mounted before the actual test procedure. The test probes are implemented in the form of test needles having associated needle carriers, which are then clamped fixed at one end in probe holders. The probe holders are then mounted on the probe holder plate in such a way that the needle tips of the test probes engage through the opening in the probe holder plate in the pattern of the contact islands on a semiconductor chip to be tested.
The intended purpose and the construction of the probers also further differ. Thus, for example, so-called vacuum probers are known, in which the testing of the devices occurs in a vacuum environment. Furthermore, subjecting the devices to be tested to specific thermal conditions is known, for example, heating them up during testing. For this purpose, the substrate carrier is equipped with a special cooling unit, which allows low temperatures or ultralow temperatures to be applied.
These known probers are used to test a plurality of different devices, such as semiconductor chips or so-called MEMS (micromechanical devices), such as sensors.
In addition, it is also possible to subject the substrate to a strong magnetic field, magnetic cores, which are powered by a superconductive coil, being situated in proximity to the substrate.
For ultralow temperature probers, which permit testing of devices on the substrate in temperature ranges of 4 K, for example, the substrate carrier is cooled by a liquid gas source, in particular from a helium tank. The relatively low vaporization temperature of helium requires on the one hand that short liquid gas lines be provided, because otherwise the helium heats up so much in long lines that it vaporizes. In addition, it is hardly possible to provide a connection line which is flexible at these temperatures. In particular when supplying the superconductor in magnetization units, fixed piping is necessary between the liquid gas tank and the magnetization unit, but also between the liquid tank and the substrate carrier. This proscribes mobility of the substrate carrier.
If devices are to be tested on a substrate, which are situated thereon in a repeat structure, which particularly all have the same contact island topography, it is necessary to manipulate the test probes from one device to the next again.
For this purpose, in a known prober from Lake Shore Cryotronics Inc., Ohio, having the name VFTT P4 Probe Station, the probe holders, which are provided with manipulators adjustable in the X, Y, and Z directions or are situated on corresponding cross tables, are to be situated outside the vacuum chamber and the test probes are to be inserted through folded bellows into the vacuum chamber and are to be positioned therein on the contact islands of the devices. The manipulation which is required again upon each approach to a new device to be tested is made easier. However, it has been shown that the folded bellows also exerts restoring forces on the test probes, and the temperature differences between chamber interior and chamber exterior strongly strain the test probes. This has the result that the positioning of the needle tips of the test probes on the devices does not have long-term stability.
In contrast, in a known cryoprober of the applicant having the name PMC 150, the probe holders together with their manipulators are situated inside the vacuum chamber. The manipulators are displaced via rotating shafts having universal joints, which are led to the outside, to adjust the test probes. This has the advantage that only three rotary bushings (one for each movement direction) are to be provided to the vacuum chamber wall per manipulator, and otherwise the movement of the test probes occurs in the interior of the vacuum chamber.
Although this prober results in long-term stability of the positioning, it does not overcome the disadvantage that upon testing of a new device, all test probes are to be adjusted to the new device.